How do I verify if an overseas buyer is genuine?

Verify before you ship, never after. Practical checks: ask for the buyer's full company name and registration number and look them up in their country's company registry; confirm they have a real website and a business email (be wary of buyers using only free email and WhatsApp); ask for trade references from other suppliers and actually call them; check that the shipping address and company address match; and do a video call to see their office or premises. The biggest red flags are: a very large first order from an unknown buyer, pressure to ship fast, refusal to use an LC or any secure payment, and most of all any request that you pay an upfront fee (for registration, agent, customs, or to release a payment). Real buyers do not ask the seller to send them money. You can also ask the Indian embassy or trade body in that country, or use ECGC to check buyer creditworthiness. When in doubt, insist on advance payment or a confirmed LC.